“In theory it should work as well or better than what we used to have,” he insisted. “But I don’t know yet.”

Less than two weeks ago, the NSA switched off its old system for collecting millions of Americans' phone records and retaining them for five years, months after receiving a mandate from Congress. The spy agency has switched to a new system in which it obtains a narrow set of records about more specific suspects from telephone companies after obtaining a court order. Phone companies tend to hold customers’ records for just two years instead of five.

Just days after the NSA reforms went into place, a married couple killed 14 people in San Bernardino, Calif., in the deadliest act of terror on U.S. soil since 9/11.

Critics of the NSA reform — including Sen. Marco Rubio (R-Fla.), who is running for president, and Sen. Tom Cotton (R-Ark.) — were quick to warn that the new limits on NSA power would negatively affect the government’s ability to investigate the attack.

“I hope the president will work with us to reverse that, so that the intelligence agencies have access to the full picture,” Rubio said on CNN this weekend.

However, the two years of records the NSA is currently able to obtain would likely cover the entire period of time that the San Bernardino shooters were married in the United States. The two killers — Pakistani native Tashfeen Malik and American Syed Rizwan Farook — met in Saudi Arabia in 2013 but appear to have been radicalized before, Comey said on Wednesday.

The White House on Wednesday dismissed the notion an intelligence failure occurred in the lead up to the attacks.

“I do think it’s still too early to make any grand pronouncements about what could have been done differently to prevent this terrorist attack from occurring," White House press secretary Josh Earnest said.

Additionally, reformers note that the new system may allow the government to obtain more people’s phone records, since reports have indicated that cellphone records were not always captured under the previous program. There are multiple other federal powers allowing the government to obtain records about people’s phone calls, details and other activity.

Rubio has seized on claims that the NSA reforms may have weakened national security as his stock has risen in the GOP nomination race. In doing so, he has attempted to paint a contrast with Sen. Ted Cruz (R-Texas), another rising presidential contender, who voted for the NSA reforms this summer.